2004 XR190

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2004 XR190
Discovery [1][2]
Discovered by first observed by:
Mauna Kea Observatory
uncredited discoverers:
R. L. Allen
B. Gladman
J. J. Kavelaars
J.-M. Petit
J. W. Parker
P. Nicholson
Discovery date 11 December 2004
MPC designation 2004 XR190
distant[3] · TNO[1] · cubewano · detached
Orbital characteristics[1]
Epoch 16 February 2017 (JD 2457800.5)
Uncertainty parameter 3
Observation arc 12.13 yr (4,432 days)
Aphelion 63.787 AU
Perihelion 51.128 AU
57.458 AU
Eccentricity 0.1102
435.54 yr (159,081 days)
0° 0m 8.28s / day
Inclination 46.732°
Physical characteristics
Dimensions 335–530 km[4]
425–850 km[5]
592 km[6]

2004 XR190 (nicknamed Buffy) is a trans-Neptunian object and possible dwarf planet, located in the scattered disc, the outermost region of the Solar System.[6] It orbits the Sun in a highly inclined, low-eccentricity orbit. The object was discovered in December 2004, by a team of researches led by Canadian astronomer Rhiannon Lynne Allen of the University of British Columbia.

Discovery and naming[edit]

2004 XR190 was discovered on 11 December 2004. It was discovered by astronomers led by Lynne Jones of the University of British Columbia as part of the Canada–France Ecliptic Plane Survey (CFEPS) using the Canada–France–Hawaii Telescope (CFHT) near the ecliptic. In 2015, six precovery images from 2002 and 2003 were found in Sloan Digital Sky Survey data.

The discovery team nicknamed 2004 XR190 "Buffy", after the fictional vampire slayer,[8] and proposed several Inuit-based official names to the IAU.


Considered a detached object,[9][10] 2004 XR190 is particularly unusual for two reasons. With an inclination of 47 degrees, it is the largest possible dwarf planet that has an inclination larger than 45 degrees,[11] traveling further "up and down" than "left to right" around the Sun when viewed edge-on along the ecliptic. Second, it has an unusually circular orbit for a scattered-disc object (SDO). Although it is thought that traditional scattered-disc objects have been ejected into their current orbits by gravitational interactions with Neptune, the low eccentricity of its orbit and the distance of its perihelion (SDOs generally have highly eccentric orbits and perihelia less than 38 AU) seems hard to reconcile with such celestial mechanics. This has led to some uncertainty as to the current theoretical understanding of the outer Solar System. The theories include close stellar passages, unseen planet/rogue planets/planetary embryos in the early Kuiper belt, and resonance interaction with an outward-migrating Neptune. The Kozai mechanism is capable of transferring orbital eccentricity to a higher inclination.[5]

2004 XR190 came to aphelion around 1901.[12] Other than long-period comets, it is currently about the thirteenth-most-distant known large body (57.5 AU) in the Solar System with a well-known orbit, after Eris and Dysnomia (96.3 AU), 2007 OR10 (87.4 AU), Sedna (85.9 AU), 2014 FC69 (84.0 AU), 2006 QH181 (83.3 AU), 2012 VP113 (83.3 AU), 2013 FY27 (80.3 AU), 2010 GB174 (70.5 AU), 2000 CR105 (60.3 AU), 2003 QX113 (59.8 AU), and 2008 ST291 (59.6 AU).[13]


2004 XR190 has a diameter estimated at around 500 kilometres (310 mi), roughly a quarter the size of Pluto, and it orbits between 51 and 64 AU (7.7 and 9.5 billion kilometers) from the Sun.

See also[edit]


  1. ^ a b c d "JPL Small-Body Database Browser: 2004 XR190" (2015-01-24 last obs.). Jet Propulsion Laboratory. Retrieved 28 February 2017.
  2. ^ "MPEC 2005-X72 : 2004 XR190". IAU Minor Planet Center. 2005-12-12. Retrieved 2014-04-06. (K04XJ0R)
  3. ^ "2004 XR190". Minor Planet Center. Retrieved 28 February 2017.
  4. ^ a b E. L. Schaller & M. E. Brown (2007). "Volatile loss and retention on Kuiper belt objects" (PDF). Astrophysical Journal. 659: I.61–I.64. Bibcode:2007ApJ...659L..61S. doi:10.1086/516709. Retrieved 2008-04-02.
  5. ^ a b c R. L. Allen; B. Gladman (2006). "Discovery of a low-eccentricity, high-inclination Kuiper belt object at 58 AU". The Astrophysical Journal. 640: L83. arXiv:astro-ph/0512430. Bibcode:2006ApJ...640L..83A. doi:10.1086/503098. (Discovery paper)
  6. ^ a b Michael E. Brown. "How many dwarf planets are there in the outer solar system? (updates daily)". California Institute of Technology. Retrieved 18 September 2016.
  7. ^ "AstDys 2004 XR190 Ephemerides". Department of Mathematics, University of Pisa, Italy. Archived from the original on 26 May 2011. Retrieved 2011-05-16.
  8. ^ Maggie McKee. "Strange new object found at edge of Solar System". New Scientist. Retrieved 2014-04-05.
  9. ^ Jewitt, David, Morbidelli, Alessandro, & Rauer, Heike. (2007). Trans-Neptunian Objects and Comets: Saas-Fee Advanced Course 35. Swiss Society for Astrophysics and Astronomy. Berlin: Springer. ISBN 3-540-71957-1.
  10. ^ Lykawka, Patryk Sofia & Mukai, Tadashi. (2007). Dynamical classification of trans-neptunian objects: Probing their origin, evolution, and interrelation. Icarus Volume 189, Issue 1, July, Pages 213–232. doi:10.1016/j.icarus.2007.01.001.
  11. ^ "JPL Small-Body Database Search Engine: H < 6.5 (mag)". JPL Solar System Dynamics. Retrieved 2014-03-27.
  12. ^ "Horizon Online Ephemeris System". California Institute of Technology, Jet Propulsion Laboratory. Retrieved 2009-03-23.
  13. ^ AstDyS-2 list of minor planets more than 57.0 AU from the Sun

External links[edit]